This invention relates to a current limiting circuit breaker and more particularly to a stationary contact arrangement for a current limiting circuit breaker.
Since their introduction, current limiting circuit breakers have enjoyed enormous acceptance and success and have become common equipment. Current limiting circuit breakers are still evolving to become better, to have higher current ratings and capacities to be manufactured in a more simple and cost effective manner. The user and manufacturer are concerned about the total cost of circuit breakers and equally concerned about the reliability of the circuit breaker and to a lesser extent the amount of space required for the circuit breaker. Accordingly, it will be appreciated that it would be highly desirable to provide a high reliability current limiting circuit breaker which occupies a minimal amount of space and is simple to manufacture.
During the past several years, circuit breakers have undergone a size reduction whereby the overall dimensions of a circuit breaker have decreased for a given rating or for a given size circuit breaker the rating has increased thereby giving greater total capacity in the same amount of space. Even with all of the tremendous size reductions that have occurred, there is always a desire to reduce the size even further or to manufacture the circuit breaker using less expensive parts and materials in place of exotic or expensive materials. Also, in current limiting circuit breakers which have blow open contacts, there is a problem with maintaining the overall size of the breaker because the length of the contacts must be sufficient to insure a sufficient blow open force. Therefore, there are conflicting interests in building a circuit breaker, to minimize the overall dimensions while insuring that current paths are sufficiently long to insure effective blow open force generation. Accordingly, it can be appreciated that it would be highly desirable to provide a compact circuit breaker which has contacts of sufficient length to develop full electromagnetic blow open forces.
It can also be understood that with increased capacity in modern circuit breakers, that there is a need to have an efficient arc extinguishing system. Generally, as the capacity of the circuit breaker is increased, the size of the arc chute must also be increased. The size of the arc chute can become a limiting factor which will cause the overall dimensions of the circuit breaker to increase. Therefore, it is desirable to provide an arc chute which does not mandate an increase in the overall dimensions of the circuit breaker.
As with the arc chute, there is a point at which the length of the contact arms becomes a limiting factor in circuit breaker size reduction. Since the arc extinguishing system contains magnetic materials, it would be highly desirable to use the arc extinguishing system in concert with the contact arms to intensify the electromagnetic blow open forces and thereby save space.
As the current rating of the circuit breaker increases, more heat and gases are generated during operation. This heat and gas must be exhausted to the exterior of the circuit breaker housing to maintain the internal temperature within the limits set for the class and size of breaker. It can therefore be appreciated that it would be highly desirable to provide a simple baffle which will allow the safe passage of blow open gases to the exterior of the breaker thereby maintaining the internal temperature of the breaker within the prescribed limits.
Accordingly, an object of the present invention is to develop a circuit breaker which has a compact stationary contact arm.
Another object is to provide a circuit breaker which has a compact stationary contact arm but which provides the required blow open forces when used in conjunction with an arc runner which intensifies the electromagnetic blow open forces.
Another object of the invention is to provide a stationary contact arrangement which has an arc runner for drawing an arc into the arc chute.
Yet another object of the invention is to provide a stationary contact assembly which is simple to manufacture and easy to assemble.